1. Field of the Invention
The present invention is directed to cookware and, more particularly, to composite roll bonded multi-ply cooking vessels containing layers of copper, aluminum and stainless steel in various combinations including, in some embodiments, a layer of silver bonded within the interior core of the composite.
2. Description of Related Art
Several prior art known constructions employing discrete roll bonded layers of copper, aluminum and stainless steel are shown in FIGS. 1 and 2 and, in themselves, are well known in the art and commercially available products marketed by All-Clad Metalcrafters LLC., the owner of the present patent application. FIG. 1 depicts a commercial line of cookware of All-Clad Metalcrafters LLC marketed under the registered trademark COP.R.CHEF. The composite cookware 1 is a three-ply bonded construction comprising an exterior layer 2 of copper bonded to a layer 3 of aluminum which, in turn, is bonded to a layer 4 of stainless steel such as austenitic 18/10 grade of stainless steel which forms the interior of the cookware 1. Copper layer 2 and aluminum layer 3 are prebonded separately and then hot roll bonded to the layer 4 of stainless steel.
The cookware 5 depicted in FIG. 2 is directed to a five-ply bonded composite comprising outer and interior layers 6 and 6′, respectively, of stainless steel roll bonded to an innermost layer 8 of copper and interfaced between the stainless steel and copper layers with layers 7 and 9 of pure aluminum. This commercial cookware 5 is sold by All-Clad Metalcrafters LLC under the registered trademark COPPER-CORE and more fully disclosed in U.S. Pat. No. 6,267,830 to Groll which is incorporated by reference herein.